Thermoplastic resin is utilized in a wide range field, such as various industrial materials, auto parts, consumer electronic appliances, and packaging materials, because it is cheap and excellent in mechanical strength, heat resistance, chemical durability, mold processability and recyclability. However, since the thermoplastic resin is flammable, many attempts have been made to make the thermoplastic resin flame-retardant. Further, a halogen-free flame-retardant thermoplastic resin composition without generating halogen gas or the like during the combustion has been suggested, as the awareness of environmental problems has been raised.
One of the representative examples of the halogen-free flame-retardant thermoplastic resin composition is a composition in which a polyolefin such as polypropylene, polyethylene or the like, or a thermoplastic elastomer is blended with a metal hydrate as a halogen-free flame-retarder. However, in order to make the molded product formed of halogen-free flame-retardant thermoplastic resin composition flame-retardant as well as the molded product formed of a halogen-based flame-retardant thermoplastic resin composition, it is necessary for the halogen-free flame-retardant thermoplastic resin composition to be blended with a large amount of the metal hydrate, as a result, the mechanical properties of the molded product, such as flexibility, abrasion resistance, low-temperature characteristics, tensile strength or elongation at break have been weakened. Therefore, keeping both flame-retardance and mechanical properties sufficient and well balanced has been required.
In order to solve the aforementioned problems, Patent Document 1 has proposed an olefin-based flame-retardant resin composition including a low-crystallinity and a flexible α-olefin homopolymer or copolymer, and a magnesium hydroxide. This technology provides a molded product with a high flame-retardance by filling a high concentration of magnesium hydroxide, a molded product which is excellent in flexibility and low-temperature characteristics, and a composition which is excellent in processability. However, even in this composition, there are still practical application problems caused by insufficient abrasion resistance and heat resistance.
Further, Patent Document 2 has proposed an abrasion-resistant and flame-retardant resin composition containing an α-olefin (co)polymer, ethylene (co)polymer, or rubber, an inorganic flame-retarder, a polymer having a carboxylic acid group, and the like. Furthermore, Patent Document 3 has proposed a flame-retardant resin composition containing a propylene-based resin, a modified styrene-based thermoplastic elastomer, and a metal hydrate, and it has been produced commercially as a substitute material of vinyl chloride resin.
However, even with the aforementioned compositions, problems of insufficient heat resistance and abrasion resistance in the molded product have remained because the low melting point materials such as ethylene-based polymer, rubber or elastomer have been used to improve the flexibility. Further, because the high-priced synthetic magnesium hydroxide having a small particle diameter is mainly used to achieve the desired characteristics, it was impossible to lower the cost of the materials and expand the sales of the materials as substitute materials of vinyl chloride resin. Therefore further improvements were required.    Patent Document 1: Japanese Unexamined Patent Application, First Publication No. S62-167339    Patent Document 2: Japanese Unexamined Patent Application, First Publication No. H5-239281    Patent Document 3: Japanese Unexamined Patent Application, First Publication No. 2002-179857